FI112556B - The method of manufacturing the electronic key or keyboard and the product manufactured by this method - Google Patents

Abstract

A method of manufacturing a pressure-sensitive electronic key or keyboard by providing a base layer (1;21) having at least one first electrically conductive area (2;241); applying at least one thin layer of a fluid piezoelectric precursor material onto the first electrically conductive area; transforming the thin layer of precursor material into an essentially coherent and uniform solid film (3) of a composite piezoelectric material firmly adhering to the electrically conductive area; forming a second electrically conductive (4;242) area spaced from the first electrically conductive area (2;241) and firmly adhering to the solid composite piezoelectric material (3) which bridges the space between the electrically conductive areas (2,4;241,242) for providing at least one essentially monolithic piezoelectric element which firmly adheres to the base layer (1) and comprises the solid composite piezoelectric material (3) with the first and second electrically conductive areas (2,4;241,242); and polarizing the composite piezoelectric material (3) with respect to the first and electrically conductive areas (2,4;241,242). <IMAGE> <IMAGE>

Description

112556

Method of manufacture of an electronic key or keyboard and a product manufactured by this method -Framställningsförfarande av en electronically tangent eller tastatur en product som har framställts med detta 5 förfarande

The present invention relates to a method of fabricating piezoelectric elements, such as touch keys or keyboards, and the resulting elements.

Most applications use piezoelectric material equipped with electrodes on each side and on which the corresponding structural element is mounted.

Examples of these types of piezoelectric keys or keyboards are described in EP 0 472 888 and CH 600 581. However, the manufacture of such components is difficult because they comprise many different components and require expensive processing to install them on the 20 structural elements. Thus, the keypad of EP 0 472 888 comprises at least two transparencies which support the strip conductors and the contact surfaces, and one piezorescence lamella for each key. To assemble the keypad, the foils and the piezo-ceramic lamina must be placed in a certain position relative to each other and glued together.

;; Although it is known to provide wire patterns by printing methods, it is presently assumed that the piezo-ceramic portion of the touch keys or keyboards cannot be fabricated except by using prefabricated element elements and that the functional stability required for the touch keys or keyboards containing the piezoelectric elements could not be achieved.

Thus, attempts to increase the efficiency and / or reduce the cost of manufacturing such keys or keyboards 35 have been limited.

The main object of the present invention is thus to provide piezoelectric elements which can be fabricated according to a method in which manual operations are significantly reduced or eliminated and where the cumbersome installation of individual piezoelectric structural elements is completely eliminated.

These and other objects are achieved according to the invention by the method defined in claim 1. Preferred embodiments of this method are described in claims 2-8. The resultant products obtained by the method and its particular embodiment are defined in claim 9.

In general, the invention provides a piezoelectric element having a structure such that manual operations can be largely omitted during its manufacture. The piezoelectric layer can be placed in its operating position in an improved manner and without the hassle of assembling and assembling individual prefabricated piezoelectric elements. Another advantage is that all required elements, such as electrically conductive layers and / or: paths, piezoelectric layer regions, and specific insulation regions can be fabricated by placing them on a substrate, carrier layer or substrate in rational, uniform and substantially similar layer formation steps. , using pre-; so called "thick-film" or "thin-film" alignment techniques, and; 30 structured coatings of substantially any shape and contour. According to the invention, piezoelectric elements of any structure, such as touch keys or keystrokes, can be fabricated. jobs, in a more economical way and in large or small series; 35 or even 112556 3 to improve them.

One particular advantage of the invention is that all components of the new components can be laid in layers by substantially similar processing steps, all of which can be automated, even when these layers have a substantially arbitrary structure. Another advantage is that in addition to conducting, insulating, and piezoelectric sandwich structures, other elements 10, such as resistors, capacitors, or diodes, can be readily implemented.

Known spacers of various types for increasing the touch sensitivity of piezoelectric keys or keyboards 15 can also be used more economically if they are made by liquid precipitation techniques and regardless of how other components of the piezoelectric structure are made.

According to a preferred general embodiment of the invention, a base or support layer containing at least one first electrically conductive region is used. A thin layer of liquid V piezoelectric precursor material is applied: to this first electrically conductive region and converted into a substantially uniform continuous solid film that is firmly adhered to the first electrically conductive region. The second electrically conductive region is formed at a distance from the first electrically conductive region adhering strongly to the solid composite piezoelectric material. This results in a substantially '*; * monolithic element at the key which adheres firmly to the base layer and includes a combined piezoelectric material; the first and second conductive regions on either side thereof, the combined piezoelectric material is polarized. The topsheet may also be used. The spacer, 4112556 as a spacer, is most conveniently used in the area adjacent to the monolithic layered element to correspond to the set of keys and to increase the sensitivity to touch in a manner known per se.

A plurality of different layers, such as electrically conductive regions, a piezoelectric layer, and - preferably - a spacer means are formed by liquid deposition techniques such as silkscreen printing.

Depending on the material used and the desired thickness of the piezoelectric material), various application and conversion steps can be performed. To further increase the thickness of the entire key structure, the first electrically conductive regions may be formed on each side of the base layer by a pair of layer structures. A bimorphic piezo-15 electrical sandwich element may also be used. The processing process is modified by forming one composite piezoelectric material on one electrode and an additional electrode on the other piezoelectric material.

The invention will be described in the following non-limiting sense. . with reference to the accompanying drawings, in which:

Fig. 1 is a schematic view of the structure of a single piezoelectric key according to the invention; Fig. 2 is a view of a structure including a plurality of keys pressed directly behind the front panel; Fig. 3 is a plan view of an embodiment of a key matrix; Fig. 4 is a side view of the keyboard matrix of Fig. 3. taken along line IV - IV; 35 5 112556

Figure 5 is a side view of the keyboard matrix taken along line V-V of Figure 3;

Figure 6 is a side view of a portion of a piezoelectric transducer;

Fig. 7 is a sectional view of a piezoelectric composite material; Fig. 8 is a view of an arrangement for corona polarization of a piezoelectric composite material;

Figure 9 is a cross-sectional view of another embodiment of a single piezoelectric key according to the present invention;

Figure 10 is a cross-sectional view of a single bimorph piezoelectric key in accordance with the present invention; Fig. 11 is a cross-sectional view of a variant of the piezoelectric key of Fig. 10; FIG. 12 is a schematic and cut away plan view of the electrodes I of a key or keypad according to the invention in a flat or "digital" arrangement on the ground floor;

Fig. 13 is a plan view of Fig. 12 after forming a piezoelectric layer 30 on an electrode pair by the liquid precipitation technique of the invention; Figure 14 is a sectional view of the structure of Figure 13.

! , 35 112556 6

Figure 1 illustrates a structure of a single piezoelectric key for a keyboard, comprising a base or base layer 1, a first conductive layer 2, a piezoelectric layer 3, a second conductive layer 4, an insulating or protective layer 5 and a bonding or spacer layer 6 connecting the key to a support film or plate 8. The hollow space 7 of the binding layer 6 is formed below the pressing point 9 which secures the key in place.

The compression directed to 10 point at 9 the force in the direction of the arrow in this case leads to bending of the piezoelectric layer 3, which generates the piezoelectric effect of an electric voltage between the conductive layers 2 and 4. The conductive layers 2 and 4 are connected to an electronic circuit which allows this voltage to be detected and transmits a keypad start signal.

In this example, the key is fabricated through a series of silk-printing steps in which the layers 2-6 are imprinted on the backing layer 1 as coatings or glued as foils. The piezoelectric layer 3 and the conductive layers 2 and 4 adhere firmly together to form a substantially monolithic piezoelectric layer element which adheres strongly to the carrier layer 1.

In this case, the typical layer thickness is in the order of 1 to 100 µm.

It should be noted that the structure of Figure 1 may vary. Thus, for example, a thin metal lamella can be used as a carrier layer 1 on which the structures are printed, as shown in Figure 2. In this case, the metal lamella 1 can be used directly as the front panel of the keyboard. According to this embodiment, it is preferable in this case to use the metal sheet 35 Mell 1 directly as a common electrode, whereby, as shown in Figure 2, the conductive layer 2 is omitted. The additional insulation layer may also be placed between the metal lamella and the conductive layer 2.

In another embodiment, the binding layer 6 and the support plate 8 may be omitted. The deflection of the piezoelectric layer is then achieved by applying an actuating force to one point on the key surface. This can be accomplished, for example, by appropriate design of the back of the front panel 1.

10

For example, in a further embodiment, the insulating layer 5 may be omitted, especially when the support plate 8 is non-conductive or has the same electrical potential as the conductive layer 4.

15

The fact that the layers to be applied can be textured also allows the application of more complex structures with a plurality of separate piezo elements on a single carrier layer. Figures 3-5 illustrate, for example, portions of a key matrix. In this case, the conductive layers 2 and 4 are made as a plurality of conductive strips in parallel rows and queues which intersect; (similarly to each other for the island-like elements of the piezoelectric layer 3.

'25: '. Figure 6 shows an embodiment of a textured element which:' ':' is capable of converting mechanical energy into electrical energy. In this case, the conductive layer 2 and the piezo layer 3 are applied as non-patterned surfaces. According to this embodiment. ; '30 the second conductive layer 4 can be patterned in the form of a strip or an islet. When the structural element made in this way is mechanically stressed, for example, by a bending stick, when fluttering like a "flag" in the wind, positive or negative charges accumulate in the islands, 35 or strips of layer 4 which can be rectified by diodes 14 112556 8 and charge capacitors 15. through. In this case, the diodes 14 and the capacitors 13 may be fixedly connected to the structural element by thin or thick film technology.

5

The electrostrictive effect following the piezo effect also permits the use of the element according to the invention in the opposite direction. In this case, the piezoelectric layer can be deformed by applying electrical voltage to the electrodes. In this way, for example, very low cost sound generators can be manufactured.

In accordance with the most preferred embodiment of the invention, a keyboard or key is manufactured using the method of FIG. 9 in the following steps: (A) A base layer 1 serves as a substrate layer forming a monolithic piezoelectric " layer "

An essential requirement for such a base layer is that it contains at least one electrically conductive region 2.

v, · This requirement can be met in a number of ways: first:: 25 and most preferred application is:: to use itself made of an organic polymer blend; ; ; an exemplary film comprising essentially an electrically insulated thermoplastic or "thermoplastic" polymer, such a thermoplastic polymer being a polymer which is not elastomeric or thermoplastic but is cross-linked by any suitable method such as "unrestricted mass" by "heat curing" .

: Typical examples include films forming commercially available polyesters, polycarbonates, polypropylene 112556 9, polyamides, polyacetals, etc., generally having a thickness of about 50 to 2000 µιη. While the flexibility of the bottom bump film is desirable, it does not need to be stretched under tensile stress. Thus, the molecular orientation of the membrane or internal crystallinity is desirable. Suitable films are resistant to aging and mechanical stress and may be translucent, transparent or opaque and / or colored. The thermal stability, which occurs at a softening temperature above 100 ° C, is a highly desirable feature as it does not limit the use of temperature that is generally required for drying, hardening, curing, or any heat treatment required to make a monolithic piezoelectric sandwich cell.

At least one electrically conductive region 2 may be formed on such organic polymer base layers either optionally (i.e., locally predetermined) or as a surface layer by conventional methods including embossing (for example, screen printing), metallization, vacuum deposition, or the like. Electricity. the conductive regions 2 and 4 and the piezoelectric material I form 'a la') the island 3 between them can have any geometric shape, for example a circle, a polygon, etc. It is only important that they lie within a limited area which rea - ',' £> 5 go to the power applied to it without crashing. 1; : Mixtures suitable for the selection of electrically conductive layers are commercially available and generally contain a binder and an electrically conductive material, such as a metallic pigment such as silver or carbon black. A specific example is the "silver paint" available from various sources. The viscosity of such paints or color inks is selected according to an appropriate application method such as screen size (as determined by conventional metric or nonmetric standards) used to apply at least one electrically conductive region (sometimes referred to as "first electrode layer" herein). to separate it from another or any later conductive layer of a key or keyboard of the invention).

The adhesive bonding between at least one electrically conductive region should be such that release during normal operation of the key or keyboard is effectively prevented.

Adhesive means, for example conventional primer layers based on ionomers, EVA resins, etc., or adhesive surface treatments, for example by oxidation or halogenation of the polymeric substrate surface, may be required or advantageously improve adhesion of at least one electrically conductive region to the substrate.

Alternatively, the base layer may comprise an electrically conductive material, such as a metal plate, which may include, but is not necessarily, a surface pattern formed, for example, by electrical organic or inorganic material.

(B) Piezoelectric precursor. An essential feature of the invention is that the piezoelectric layer or layers 3 of the new key or keyboard are not prefabricated in the same way as previously known keyboards ,; V but that it or they are formed in at least one electrically conductive region and adhere firmly thereto (this region again adhering strongly to the ground layer). As mentioned above, the term "strong grip" is used herein in parallel with the phrase "non-removable by peeling under operating conditions during the life of a key or keyboard." It has been found that this feature can be achieved according to the invention and is believed to be essential In addition, each layer of the 3: 5 key or keyboard according to the invention must be uniform.

The term "precursor", as used herein to designate a uniform layer (or layers) of Piet-5 socio-electric material formed in accordance with the invention, means any system capable of existing in a non-solid, i. fluid state and can be applied as a thin film (the term "thin ·· generally denotes an order of magnitude of 1 to about 100 μπι, with a solid-10 thickness preferably less than 20 μπι). Figure 7 illustrates a composite system that can be applied by printing techniques. In this system, the powdered piezoelectric ceramic material 10 is suspended in the binder 11. The hardness of the binder should be as high as possible so that the forces can be transferred to the granules as efficiently as possible.

The preferred precursor comprises a "piezoelectric paint", a term generally referred to as a liquid system containing or having a fine piezoelectric component. Such solid materials are generally of the PZT type (lead zirconium titanium) and are commonly referred to as "ceramic" piezoelectric materials. They are commercially available from various sources. Typical particle sizes for such piezoelectric solids are from about 0.5 to about 20, preferably from 1 to 10, and preferably from about 1 to about 5. The lower limit * * depends more on the availability of effective products than on the value of the invention. Again, the upper limit is believed to be essential for most embodiments of the invention, the solid layers formed by such materials; ; for consistency and uniformity.

The concentration of the piezo-ceramic powder is selected to ensure mechanical contact between as many as 12,115,556 as many ceramic fragments as possible, which is generally in the order of 0.1 to 10 volume ratio of ink base material or solvent to ceramic material. This is needed to ensure that the transmission to the granules is as efficient as possible. In this case, the ceramic content is limited by the requirement for adhesion and mechanical resistance of the dried material.

Although other than "ceramic" solids, for example, fine crystalline organic materials such as normally solid organic acids or their salts, for example tartaric acid, tartrates, salicylates, and saccharides, polyvinyl or polyvinylidene halides, etc., may be used herein, their use being related herein. 15 desirable for most purposes.

The term "fluid" as used herein refers to precursor material containing liquid or gaseous spaces or systems. Liquid systems 20 are generally desirable in this context, mainly for practical reasons related to simple handling, availability, and relative ease of process control.

; Representative examples include one or more finely divided solid piezoelectric dispersions in a liquid or paste, such as commercially available substrates, "solvents" or "varnishes" for screen printing. Such bases generally contain one or more solvents and one or more binders, e.g. organic solvents dissolved in suitable solvents. Polymers or, optionally, additives and excipients, for example, for controlling evaporation or cure rates, etc.

Examples of other liquid or gaseous systems include substances that can be deposited by metallization 112556 13 or various precipitation techniques, i.e. substances capable of forming a piezoelectric solid from a gaseous or liquid precursor such as zinc oxide, etc.

5 (C) Precursor Use. The technology for using the precursor will, of course, depend on the type of precursor system used. In the case of a preferred liquid system, pre-frost films can be precipitated by screen printing, spraying, roller coating, etc. Such liquid systems can be used, and most preferably so, by precipitating a thin film set as defined above, preferably with an intermediate solidification such as drying, quenching or curing. The spacer 16 provided with apertures 15 for the precursor 15 may also be formed by embossing or may comprise a formed and textured layer provided with the aperture 14. The spacer may be applied before the precursor and may be used in the application process or after application of the precursor. The spacer is preferably non-compressible to prevent crosstalk.

: * · · '(D) Precursor conversion. Here, too, the technology for converting the precursor depends on the system in use. In the case of recommended liquid systems. '. *. 25, conversion is accomplished by solidification; for example, removing the liquid phase by drying, quenching or curing. For multiple purposes, the term ,,. • Converting methods are desirable as long as they do not damage other components. Temperatures in the range of about 50 ° C to about 200 ° C are typical. Multiple purposes; for this purpose, it is desirable that the resulting uniform layer has a thickness of less than about 125 μπι and preferably less than 100 μι. A particularly desirable thickness value is even lower, less than * 75 μπι, and preferably less than about 50 μπι. However, the layer must be uniform in the sense described above and may require repeated application and solidification depending on the components used, mainly depending on the resilience of the polymer matrix containing the finely divided solid piezoelectric material.

5As noted above, the resulting layer should be substantially "uniform". This concept generally implies that a uniform piezoelectric layer must prevent short-circuiting of adjacent electrode layers.

10 A common reason for the lack of uniformity of the layers caused by the solidification of the liquid or pasty system are small, directly microscopic air bubbles. A conventional means of avoiding these air bubbles is degassing, for example by means of reduced pressure. Another method of achieving or improving the uniformity and uniformity of the piezoelectric layer is by applying mechanical or hydrostatic pressure.

The best possible results can be achieved with a particular system by carrying out a few simple experiments, such as measuring the electrical performance of the layers, preferably after both adjacent electro-V 2 layers 4 and 4 have been formed.

1 · 1: 2 5 The term "combined" as used herein in accordance with the invention; 'j'; in its unitary piezoelectric film, is intended to include any layer system formed by a plurality of solid components, regardless of the type of bonding. This includes the surface sizing that occurs in the layer formed by electrodeposition as well as; when using adhesives or adhesives. A suitable way of gluing piezoelectric constituent particles together is by "matrix", i. formation of an inorganic or, preferably, organic material, such as a polymer, which may or may not be cross-linked. Such a matrix provides a substantially continuous phase and holds the solid components of the piezoelectric material firmly together while preventing adverse changes in the layer under long-term mechanical stress (e.g., two or four million key presses) and aging (as determined by acceleration test, such as use at high temperatures, which are expected to last for several years).

In this context, it should be noted that it is astonishing to see that the invention can provide keys or keyboards that meet such stringent requirements. The two main objects of the invention can thus be achieved, namely, a significantly improved economy of manufacture and an equally good or improved performance.

(E) Alternate second electrode layer. Upon completion of step (D), a second electrically conductive layer 4 (second electrode layer) is applied over a film of composite piezoelectric material 3, as shown in Figure 10. This can generally be accomplished as described above in step (A), wherein the first electrode layer 2 is formed on the electrically insulating substrate layer and no further explanation is required. Protective or; An insulating layer such as layer 5 may be formed on top of this second electrode layer 4.

(F) Polarization or Polarization. As is known in the art, exposure to an electrical voltage or field is generally required to activate a contact element * ** containing a piezoelectric material. Typical Conventional Polishing Methods: Can be applied in this context by applying a voltage to the ·. 2 and 4. The ferroelectricity of the electric field. the inside must be large enough to cross the coercive field of 35. This is particularly important when the relative dielectric constant of the ferroelectric 112556 16 is much higher than with the binder material, which results in a corresponding reduction of the applied electric field within the ferroelectricity.

By lowering or increasing the temperature during the polarization process, it is also possible to reduce the relative dielectric constant and coercive field of the ferroelectricity, thereby facilitating polarization. Polishing is preferably performed at elevated temperatures (e.g., 80-150 ° C) when the piezo-10 electrical material is incorporated into the polymer matrix. Pressure may or may not need to be applied simultaneously.

In addition, the polishing may be carried out before or after the overlay and any additional support layers, such as mainly rigid mounting plates 8, are applied.

To avoid fractures between electrodes during the polarization process, polarization can be accomplished by corona polarization. This occurs after solidification of the piezo material 3 but before the second electrode layer 4 is applied. In this case, as shown in FIG. 8, the first conductive layer 2 is connected to ground or to a ground potential. Thereafter, the electrode needle 12, located about 25 cm from the substrate layer, is connected to a high voltage source 13. The resulting corona discharge leads to surface charges of the piezo material, thereby polarizing this material.

v30 Various polarization techniques, particularly electrode dipolarization, allow the piezo-material to be polarized only at high, ·· *, expensive desired locations, thereby reducing inductive interference between adjacent regions.

Another piezoelectric material comprises a suitable piezoelectric 11255617 polymer such as polarized polyvinylidene fluoride (PVDF). In this case, the polymer is pressed either in dissolved form or above a melting point of 160-180 ° C. The material may also be applied, for example, by means of an electrostatic jet-5 jet injection method. After application, it is polarized by an electric field, whereby the above methods can be used. This must be done above the glass temperature or when the film is not yet dry.

It is also possible to use this type of polarized film, in which all other layers are applied, for example, by printing techniques.

As shown in Figure 9, the joint thickness of the piezo material 3 and the electrically conductive layer 4 is less than the thickness of the spacer 16. Thereby a gap is formed below the layer structure allowing it to bend like the binder layer 6 of Figure 1. Conventional spacer means may include, for example, a piece of cardboard or plastic having apertures in accordance with the keyboard pattern 20. Reference is made to EP-A-0 472 • 888, the disclosure of which is incorporated herein by reference. Various means are also known in the art: for sealing the topsheet, which may but need not be of the same type as the base sheet in its preferred form as an organic polymeric film.

The spacer generally forms a small hollow space under each key, with the piezoelectric layer supported on its circumference but without support or less supported in the central portion. 30, so that the pressing pressure on the top of the keypad provides a bending tension to increase the electrical signal. Since this feature is known in the art, it is not necessary to explain it further in this context.

35 It is also known in the art of piezoelectricity that the keys 18 11? R R 6

! I L ·. yj \ J O

or keyboards may have so-called. bimorphic structure. This can be accomplished in an improved manner according to the invention by repeating steps (C) - (E). As shown in Figure 10, the monolithic piezoelectric 5 layer structure of this embodiment contains two uniform films 3A and 3B of solid piezoelectric material between the first and second electrode layers 2,3, separated by an intermediate "third" electrode layer 17. Other interlayer layers may also be used to improve adhesion, cohesiveness or compatibility of adjacent layers.

Another embodiment of a multilayer piezoelectric material embodiment is shown in Figure 11. This embodiment increases the thickness of the layer structure 15 without compromising the cohesiveness of the piezo material. The bottom IA includes first electrode layers 2A and 2B on each side. The islands 3A and 3B of the piezoelectric material are formed on the respective first electrode layers IA and IB and the second electrode layers 4A and 4B 20 are formed on the islands 3A and 3B.

In all embodiments of the invention, the key or key system should include a stable "monolithic" structure of the piezoelectric sandwich element ν, ί, i.e.. multilayer structure,:! 25 comprising a base layer, an electrode layer, and a piezoelectric film layer in the form of a unitary structure, ... in which the layers adhere to one another in a manner obtained by applying the layers from their respective precursors, i.e.. using compounds or materials containing or providing the required ingredients in a system comprising a fluid rather than a solid material and thus not used as a prefabricated element.

The following examples illustrate without limitation one preferred embodiment of the invention. Quantities and percentages are by weight 112556 19 unless otherwise stated.

Example I: 5 A touch pad was manufactured as follows: (a) Base layer The base layer for keyboard manufacturing consisted of a commercially available polyethylene terephthalate cal-10 (thickness 175 μπι, trade name Melinex, type 505 ST, supplied by ICI) containing conventional priming or chlorinated to improve infection.

15 (b) First conductive layer

Commercially available silver paint (sold, for example, by Ac-heson Industries USA or Olin Hunt UK) was applied locally to the base layer by screen printing (screening standard 90T equivalent to 230 T mesh) of about 7.5 µιη: η (dry) thickness - .20 della type known per se. made of 16 key regions and a first wired '·' path pattern for individual or group connections (line / line). The pattern was obtained in a conventional manner related to photography with 16 circular electrode regions and their joints. '25 to form wiring paths. The printed pattern was air-dried at 110 ° C for 20 minutes.

(c) Piezoelectric layer ... Printing ink was prepared by grinding in a laboratory mill '.30 using the following composition: •' * · 100 parts of commercially available PZT type ceramic

'Powder (sold by Philips, The Netherlands, Type PXE 5 or Type PXE

; . 520), particle size in the order of 0.5 to 2.5 micrometers; '. 20 parts commercially available screen printing varnish (sold by 35 Printcolor, Switzerland under the name of resin 290-05); 112556 20 5 parts acrylic lacquer (Printcolor, type 290); 1 part evaporation retardant (Printcolor, type 10-, 99);

The powder was repeated three times with screen printing to achieve conventional homogeneity (visual inspection) and viscosity.

The ink was applied locally to the bottom layer by triplicate printing according to step (b) over the area of the electrode sections made with a 43 T (110 mesh T) screen, carefully avoiding the formation of air bubbles in the area. The pattern produced by photographic photography was used to concentricize the electrode areas made according to (b) with a margin overlap of about 1 mm. The layer formed after each printing operation was air dried for 30 minutes at 100 ° C. The resulting dried Piet-electrode film had a thickness of about 50 µπι.

(d) Second electrode layer Mainly according to (b), the electrode pattern and the like. With 20 interface path boundaries for the individual activation of each key, areas of (b) and (c) were screen-printed using a 120 T (305 mesh T) W screen using the method described in (b). i tua pattern. The printed layer was air dried for 20 minutes / 25 at 110 ° C.

(e) Protective layer

The protective layer was applied to the ends of the terminals by means of ultraviolet rays using a polymerizable lacquer layer. 30 T (sold by Olin Hunt, Type UV) 120 T screen (305 mesh); '··. Irradiation by actinic UV irradiation was performed using a commercially available UV lamp.

(f) Polishing 35 The product obtained in (e) was heated to about 150-125,556 at 21 ° C between two pressed plates (0.0 bar) and a voltage of 100 V DC was applied between each pair of electrodes via conductor paths. Polishing was continued for 10 minutes.

5 (g) Topcoat and Outer Fitting

A 125 µπι sheet of polyethylene terephthalate was fixedly bonded to a sheet of paper having apertures substantially corresponding to the electrode pattern to form a disc-shaped hollow space below each of the two electrodes and the interstitial layer of the piezoelectric layer. This sheet was aligned with, and firmly attached to, the polarized product using a commercially available binder, such as Adhesive Type 467 sold by 3M (Minnesota, Mining and Manufacturing Co.). The final product provided a maximum signal strength of about 10V.

Example II:. 20 The keypad was manufactured as follows:; '(a) Ground floor Ground floor for manufacturing keyboards; consisted of a commercially available polyethylene terephthalate calcium, 25 von (thickness 175 μπι, trade name Melinex, type 505 ST, supplied by '<, «·' ICI), containing a conventional primer coat or was chlorinated on both surfaces in the usual manner to improve adhesion.

* 30 (b) Conductive base layers; "The same silver paint was applied locally to the municipal side of the base layer IA as in the first conductive layer of Example I. Fig. 2A, 2B showing the 16 key areas and the conductive paths connecting them to both sides of the base 35 layer.

112556 22 (c) Piezoelectric layers

The piezoelectric printing ink was prepared in the same manner as in Example I. The ink was applied by silkscreening on both sides of the base layer to an area of 16 conductive key regions made in accordance with (b). The printing was repeated three times, as in Example I, also by overlapping the key regions prepared in (b). Again, the resulting film 3A, 3B had a total thickness of about 50 µιη.

10 (d) Conductive Coatings

The electrode pattern was applied to the same piezoelectric layers on both sides of the base layer as in the second electrode layer 4A, 4B of Example I.

15 (e) Protective layers

The sealing layer for the protection and electrical insulation of the layer structure made in (a) to (d) was applied to both sides of the base layer in the same way as the protective layer of - · 20 according to Example I.

(F) Polishing '' For the polishing of the resulting bimorphic structure according to (a) to (e), the conductive base layers 2A and 2B of all 32 layer elements were connected in series. : teen. The outer conductive layers of the 16-layer element 4A on one side of the base layer were joined together, and the conductive region of the layer 4B on the other side was also joined. together. A 200 V DC voltage was applied between the two outer conductive layers 4A, 4B and the product was heated to 150 ° C. Polishing was continued for 10 minutes. During polishing, those on both sides of the ground floor. the layer elements were connected in series. After polishing, the two respective layer elements were joined in parallel by joining 35 of their conductive base and outer layers.

23 112556 (g) Topcoat and Outer Fitting

A 125 µιη sheet of polyethylene terephthalate was fixedly bonded to a sheet of paper having apertures substantially corresponding to the electrode pattern to form a disc-like hollow space beneath each of the two electrodes and the interstitial piezoelectric layer. This sheet was aligned with and firmly attached to the polarized product using a commercially available binder 10 such as adhesive type 467 sold by 3M (Minnesota, Mining and Manufacturing Co.). The final product provided a signal strength of about 10 V max.

Example III

This example illustrates a preferred embodiment for manufacturing a spacer device for a key or keypad of the invention, instead of using a prefabricated fluid precipitation technique.

.20

Example I was repeated except that the spacer line, i. spacer layer 16 (Figure 9) was applied by pressing prior to step (d) to form a layer having a total thickness of about 100 µπι. The printing may be carried out in the manner described in Example 25 (I) (c) except that the ceramic material to be added to the ink base is replaced by the "neutral" component described below. Alternatively, the interlayer layers may be prepared in accordance with the invention by printing a pattern using, as above, an UV-curing polymer ink or a reactive polymer blend such as commercially available epoxide polymers in combination with suitable curing agents, for example Araldi. when such a polymer is also required to be "neutral".

35 112556 24 This is explained as follows. Each component of the spacer or layer formed by the precipitation of the fluid according to the invention should preferably be "piezoelectrically neutral", this expression being based on 5 conventional piezoelectric deformation constants, generally expressed as picoCoulombs / Newton (pC / N), recognizing as? impulse direction mechanical deformation in the form of subindices "d ^", for example d31. Thus, the material used as a constituent of each interlayer 10 must include a piezoelectric deformation constant that does not exceed about one percent (numerical basis) of the piezoelectric deformation constant of the appropriate piezoelectric layer, e.g., d31 (layer 16) ¥ <0.01 d31 (layer 3).

The ink suitable for the spacer layer can be applied as a single application step, provided that it has sufficient consistency or composition, i. if it is obtained, for example, by using a solvent - free polymer blend -. 20 or a filler such as usually glass powder or other particulate solid which is "neutral" in the sense mentioned above and also in the normal chemical sense. Several inorganic silicates, carbonates and. oxides meet this requirement and are usable. • 25 Recommended particle sizes less than 50 μια, for example, up to 30 μια.

! V. Example IV

t; . Example II is repeated with the exception that the lithographic lining lines 16A, 16B (Fig. 10) are produced by printing using glass from powder (particle size less than about 20 μπι) and commercially available basic ink such as Example I (c),. 2: 3, i. e. containing about 35% by weight of glass-35 powder.

112556 25 Spacer layer 16A is applied after forming the first piezoelectric layer 3A by pressing and before forming the third electrode layer 17. The spacer layer 16B is applied with the same ink as the layer 16A but after forming the second piezo-5 electrical printing layer 3B and before forming the electrode layer 4.

Example V

Essentially, the process described in Example III was repeated to produce a key or keyboard structure similar to that shown in Figure 11. Starting from the base layer IA, the first "layer structure" is formed thereon by successively applying a conductive electrode layer 2A, a piezoelectric layer 3A, a spacer layer 16A and an electrode layer 4A. Thereafter, a second layer structure 15 was formed on the opposite side of the base layer IA by successively applying conductive electrode layer 2B, piezoelectric layer 3B, spacer layer 16B, and electrode layer 4B. The topsheet IB was then applied as in Example I. Of course, the order of fabrication of these two layer structures could also be *: reversed by starting with the application of the electrode layer 2B to the opposite side of the base layer IA.

Example VI

The key or keypad having the structure shown in Figures 12 to 14 was made according to the invention as follows. The base layer 21 was formed by screen printing according to Example I or using vacuum deposition (or any other technique suitable for forming relatively thin electrically conductive layers on a polymeric substrate), together with an electrically conductive pattern, as with conventional numerically spaced transducers. , '' this pattern comprises two electrodes 241, 242 located at a distance from one another '*, which: '35 each include an interface path 243, 244.

112556 26 A piezoelectric layer 23 is then applied in the same manner as in Example I, paragraph (c). For illustrative purposes, layer 23 is not shown with side overlap but without fully covering electrodes 241, 5 242. However, this is not critical and for multiple purposes it is desirable that layer 23 substantially or even overlap electrodes 241, 242. The spacer layer 26 is then formed as described above, and further processing to obtain the desired final product 10 can continue.

Polishing can be accomplished by applying an electric field applied between each pair of electrode arms 241, 242 via conductive paths 243, 244. Part of the field penetrates the piezoelectric layer 23 and causes polarization in the region around the branches.

When the mechanical stress is applied to the touch sensitive area of a key or keyboard made in this way, 20 i. in the space between the electrode layers of the same level, provided with a co-operating piezoelectric layer t ', an electrical signal of generally about 5 V is generated between the electrodes 241, 242. This signal can be: processed as in FIG. 6.

; 't25. Persons skilled in the art of piezoelectric keys or keyboards may make a variety of variations within the scope of the invention - keyboards represent repetitions of ·' keys and include the required wiring 10, 26, 48, or v 30 more any symbols such as alphabet letters: ·· *, the symbols used in the system controlled by the keypad, in a particular pattern.

For example, a number of other piezoelectric materials could be used and dispersed as mixtures containing a fluid precursor (liquid or gas) precursor system comprising materials suitable for forming a uniform piezoelectric layer. For example, the polymer contained in the above-mentioned matrix of composite piezoelectric layers could be piezoelectric active instead of neutral. Levi printing techniques other than silkscreen printing, such as spraying, brushing, dipping coating, etc., may also be used, provided that the local patterns required for piezo-electric keys or keyboards can be obtained by commercial manufacturing such that substantially automatic assembly of all components is achieved. in the manufacture of keys or keyboards 15.

Claims (9)

A method of producing a pressure-sensitive electronic key or keyboard, characterized in that it comprises the following steps of: producing a base layer (1; 21) having at least one first electrically conductive region (2; 241), applying at least one thin layer of fluid comprising an organic polymer and a particulate piezoelectric material as a precursor material in said at least one first electrically conductive region, transforming said at least one thin layer of said precursor material into a substantially coherent and uniform solid film (3) of composite material of piezoelectric material in a matrix of a polymer adhered to said first electrically conductive region; forming a second electrically conductive region (4; 242) spaced from the first electrically conductive region (2; 241) upon solid bonding to the solid film of the composite material of the piezoelectric material disposed in: the matrix and forming a bridge over a space between the electrically conductive regions 30 (2,4; 241,242) to provide at least one substantially monolithic piezoelectric element which adheres to said base layer and comprises the said solid film of the composite. Put the material of the piezoelectric: material (3) into the matrix with said first and second electrically conductive regions (2.4, -241,242), 112. h ('32 ..... and polarize the piezoelectric material (3) ) arranged in the matrix in relation to said first and second electrically conductive regions (2,4 / 241,242). Method according to claim 1, characterized in that the base layer (1) comprises a film of an organic polymer composition with an electrically conductive layer (2) applied to at least one locally predetermined area 10 on one side of said organic polymer film by fluid. deposition technique, and that a thin layer of precursor material is also applied by fluid deposition technique. Method according to claim 2, characterized in that the fluid deposition technique is a silk screen printing technique. Method according to any of claims 1-3, characterized in that said step before polarization is repeated to form a bimorphic piezoelectric sandwich element 20 comprising two superposed, continuous solid films of said composite piezoelectric material separated by a third electrically conductive layer bonded together said superposed films of said composite piezoelectric material. ί 25 5. A method according to claim 4, characterized in that: said base layer has at least one first electrical conductor. area on either side thereof and that the steps prior to polarization are performed on the first electrically conductive region on each side of said base layer. Method according to any one of claims 1-5, characterized in that it comprises forming at least one spacer in an area adjacent to said at least one: monolithic piezoelectric element. 33 112556 Process according to claim 6, characterized in that the spacer is formed by pressing. 8. A method according to claim 7, characterized in that the spacer is formed by pressing the piezoelectrically neutral material consisting of the layer. A mechanically stable and aging resistant pressure-sensitive electronic key or keyboard comprising a monolithic piezoelectric element, characterized in that said monolithic piezoelectric element comprises two superimposed continuous solid films of said composite piezoelectric material separated by a third electrically conductive spaced apart electrically conductive surface. with both said superposed films of said composite piezoelectric material.